Compressor housing for turbocharger and method for manufacturing the same

ABSTRACT

A compressor housing for a turbocharger including a refrigerant flow path and a recirculation part, which is dividably composed of a scroll piece and a shroud piece. The refrigerant flow path is formed as an annular space that is defined by a first flow-path formation part of the scroll piece and a second flow-path formation part of the shroud piece that are fitted with each other. In the refrigerant flow path, a first press-fitting portion of the shroud piece is press-fitted into a first press-fitted portion of the scroll piece to form an inner circumferential seal part, and a second press-fitting portion of the shroud piece is press-fitted into a second press-fitted portion of the scroll piece to form an outer circumferential seal part. The recirculation part recirculates part of the air which has reached the shroud part to an upstream of the compressor impeller.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority under 35 U.S.C. § 119 to Japanese Application No. 2019-026413, filed on Feb. 18, 2019, entitled “COMPRESSOR HOUSING FOR TURBOCHARGER AND METHOD FOR MANUFACTURING THE SAME”. The contents of this application are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure relates to a compressor housing for a turbocharger and a method for manufacturing the same.

Description of the Related Art

A turbocharger to be mounted on an internal combustion engine of an automobile, etc. includes a compressor impeller and a turbine impeller, which are housed in a housing. The compressor impeller is disposed in an air flow path that is formed inside the housing. The air flow path is provided with an intake port for sucking in air toward the compressor impeller, a diffuser passage through which compressed air discharged from the compressor impeller passes, and a discharge scroll chamber into which the compressed air passing through the diffuser passage flows. The discharge scroll chamber discharges the compressed air into the internal combustion engine side.

Some internal combustion engines for an automobile, etc. are provided with a positive crankcase ventilation system (hereinafter referred to as PCV) for purifying the inside of a crankcase and/or a head cover by reflowing blowby gas that has generated in the crankcase. In such a configuration, oil (oil mist) contained in the blowby gas may flow out from the PCV into an intake passage that is located upstream of the compressor in the turbocharger under some circumstances.

At that time, if air pressure at an outlet port of the compressor is high, air temperature there is made high, so that the oil flowing out from the PCV is concentrated and thickened by evaporation to have high viscosity. In some cases, the oil is accumulated as deposit on, for example, the diffuser surface of a compressor housing for a turbocharger and/or the surface of a bearing housing which opposes the diffuser surface. And, there is a risk that the deposit thus accumulated may narrow the diffuser passage to thereby cause reduction in performance of the turbocharger and reduction in output of the internal combustion engine.

In the past, the air temperature at the outlet port of the compressor was controlled to some extent to prevent such deposit accumulation in the diffuser passage as described above. As a result, a turbocharger was not able to satisfactorily exhibit its performance, and the output of an internal combustion engine was not satisfactorily raised.

Patent Document 1 discloses a configuration to prevent deposit accumulation in a diffuser passage, in which a refrigerant flow path is provided inside a compressor housing for a turbocharger to allow a refrigerant to pass therethrough, thereby inhibiting an increase in the temperature of compressed air passing through an air flow path inside the housing. In the configuration disclosed in Patent Document 1, the compressor housing for a turbocharger is composed of a first piece, a second piece, and a third piece, and these components are assembled to one another to define the refrigerant flow path.

PRIOR ART LITERATURE Patent Document

Patent Document 1

-   -   JP-A-2016-176353

SUMMARY OF THE INVENTION

However, in order to keep liquid-tightness of the refrigerant flow path, the configuration disclosed in Patent Document 1 needs to form a holding portion for holding an O-ring serving as a sealing member between the first piece and the second piece and to fit the sealing member into the holding portion, and in addition, to hold the sealing member by the first piece and the second piece. Thus, parts count is indispensably increased, which causes increase in manufacturing cost and reduction in assembling workability.

Further, in the configuration disclosed in Patent Document 1, each piece is formed in a shape having no undercut part in view of mold releasing in order to mold the piece by die casting. The cross-sectional shape of the scroll chamber is far different from a circle form accordingly, and such a shape causes reduction in compression efficiency of supplied air.

As a method to form the refrigerant flow path in the compressor housing for a turbocharger, it is conceivable to use gravity casting with a sand core. In this method, high flexibility in shape can be expected to thereby meet complicated shapes. On the other hand, this method requires long casting cycle, and needs a sand shakeout operation for removing the sand core and an inspection work for checking remaining casting sand. Therefore, the number of manufacturing processes is increased, and the productivity is reduced accordingly.

Furthermore, according to the configuration of Patent Document 1, the refrigerant flow path thus provided serves to prevent deposit accumulation, so that the flow rate of the compressor impeller can be increased to thereby increase the maximum output of an engine owing to the high supercharging thus attained. Meanwhile, the increased flow rate of the compressor impeller and the unfavorable cross sectional shape of the scroll chamber cause reduction of low-speed torque in an engine.

The present disclosure has been made in view of this background, and is directed to a compressor housing for a turbocharger in which sticking of deposit is prevented, satisfactory assembling workability is achieved, molding can be easily made by die casting, so that the performance on the high airflow-rate side is improved while the performance on the low airflow-rate side is maintained at low cost.

Means for Solving the Problems

One embodiment of the present disclosure provides a compressor housing for a turbocharger configured to house a compressor impeller, the compressor housing including:

an intake port formation part that defines an intake port configured to suck in air toward the compressor impeller;

a shroud part that surrounds the compressor impeller in a circumferential direction and has a shroud surface facing the compressor impeller;

a diffuser part that is formed on an outer circumferential side of the compressor impeller in the circumferential direction and forms a diffuser passage configured to allow compressed air discharged from the compressor impeller to pass therethrough;

a scroll chamber formation part that forms a scroll chamber configured to guide the compressed air passing through the diffuser passage to outside;

a refrigerant flow path that is formed along the diffuser part in the circumferential direction, and allows a refrigerant for cooling the diffuser part to pass therethrough; and

a recirculation part configured to recirculate part of the air which has been sucked in from the intake port and reached the shroud part, to an upstream of the compressor impeller,

wherein the compressor housing is dividably composed of a scroll piece including at least part of the intake port formation part and at least part of the scroll chamber formation part, and a shroud piece including at least part of the scroll chamber formation part, the diffuser part, and the shroud part, and being press-fitted into an inner side of the scroll piece in a shaft direction,

wherein the refrigerant flow path is formed as an annular space that is defined by a first flow-path formation part of the scroll piece and a second flow-path formation part of the shroud piece, the first flow-path formation part and the second flow-path formation part being formed respectively at each opposing part of the scroll piece and the shroud piece which oppose each other,

wherein the first flow-path formation part and the second flow-path formation part are fitted with each other at an inner circumferential seal part configured to seal the refrigerant flow path on the inner circumferential side of the refrigerant flow path and at an outer circumferential seal part configured to seal the refrigerant flow path on the outer circumferential side of the refrigerant flow path,

wherein the inner circumferential seal part is formed by press-fitting a first press-fitting portion of the shroud piece into a first press-fitted portion of the scroll piece,

wherein the outer circumferential seal part is formed by press-fitting a second press-fitting portion of the shroud piece into a second press-fitted portion of the scroll piece, and

wherein the recirculation part includes: a recirculation chamber as a space that is defined by a first recirculation chamber formation part of the scroll piece and a second recirculation chamber formation part of the shroud piece, the first recirculation chamber formation part and the second recirculation chamber formation part being formed respectively at each opposing part of the scroll piece and the shroud piece which oppose each other; a communication part that is open at the shroud surface and is communicated with the recirculation chamber; and a blowout part that is open at the scroll piece, or in an upstream position of the compressor impeller of the shroud piece, and is communicated with the recirculation chamber.

Effects of the Invention

According to the compressor housing for a turbocharger as the one embodiment of the present disclosure, the compressor housing for a turbocharger is dividably formed, and the refrigerant flow path is defined by the first flow-path formation part and the second flow-path formation part. The first flow-path formation part and the second flow-path formation part are formed respectively at each opposing part of the scroll piece and the shroud piece which oppose each other. The refrigerant flow path is sealed at an inner circumferential seal part on the inner circumferential side of the refrigerant flow path and at an outer circumferential seal part on the outer circumferential side of the refrigerant flow path. The inner circumferential seal part is formed by press-fitting the first press-fitting portion of the shroud piece into the first press-fitted portion of the scroll piece, and the outer circumferential seal part is formed by press-fitting the second press-fitting portion of the shroud piece into a second press-fitted portion of the scroll piece. The recirculation chamber of the recirculation part is formed of a space that is defined by a first recirculation chamber formation part of the scroll piece and a second recirculation chamber formation part of the shroud piece. The first recirculation chamber formation part and the second recirculation chamber formation part are formed respectively at each opposing part of the scroll piece and the shroud piece which oppose each other. Such configurations make it possible to seal the refrigerant flow path on the inner circumferential side of the refrigerant flow path and on the outer circumferential side of the refrigerant flow path while forming the recirculation part only by press-fitting the shroud piece into the scroll piece to assemble the both. Consequently, it becomes unnecessary to interpose an O-ring between the first flow-path formation part and the second flow-path formation part, and the assembling workability is satisfactory. Further, because the O-ring itself is not necessary, reduction of the parts count can be achieved. In addition, the refrigerant flow path provided in the compressor housing for a turbocharger makes it possible to restrain deposit accumulation in the diffuser passage to thereby achieve high supercharging on the high airflow-rate side of the compressor (at high speed rotation side of an engine) and to increase the maximum output of the engine.

In addition, the recirculation part can recirculate part of the air that has reached the shroud part, to an upstream side of the compressor impeller, and constitutes a so-called casing treatment. Accordingly, even when the flow rate of the compressor impeller is made largely increased in response to high supercharging, the operation range on the low airflow-rate side can be maintained and reduction of the low-speed torque can be prevented. In other words, the compressor housing for a turbocharger makes it possible both to maintain the low-speed torque, which is owing to the fact that the operation range on the low airflow-rate side is maintained by the recirculation part, and to increase the maximum output, which is owing to the fact that the refrigerant flow path brings about high supercharging.

Further, the compressor housing for a turbocharger is dividably formed and includes the scroll piece and the shroud piece. The scroll chamber is formed by assembling at least both the pieces to each other. Such a configuration makes it possible to form the scroll chamber with a circular cross section while forming the scroll chamber formation part in a shape having no undercut part, which enables mold releasing. As a result, the scroll chamber can be more easily formed by die casting while the compression efficiency for the supplied air can be improved.

As mentioned above, the one embodiment of the present disclosure can provide a compressor housing for a turbocharger in which sticking of deposit is prevented, satisfactory assembling workability is achieved, molding can be easily made by die casting, and high supercharging is achieved at low cost.

It is noted that the reference numerals throughout the specification correspond with the specific means which are described in the embodiments described later, and are not to limit the technical scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a compressor housing for a turbocharger according to Embodiment 1.

FIG. 2 is a conceptual diagram for explaining a method for manufacturing the compressor housing for a turbocharger according to Embodiment 1.

FIG. 3 is a cross-sectional perspective view of a scroll piece according to Embodiment 1.

FIG. 4 is a perspective view of a shroud piece according to Embodiment 1.

FIG. 5 is a cross-sectional perspective view of the shroud piece according to Embodiment 1.

FIG. 6 is another conceptual diagram for explaining the method for manufacturing the compressor housing for a turbocharger according to Embodiment 1.

FIG. 7 is a partly enlarged cross-sectional view of the compressor housing for a turbocharger according to Embodiment 1.

FIG. 8 is a cross-sectional view of a compressor housing for a turbocharger according to Modification 1.

FIG. 9 is a conceptual diagram for explaining a method for manufacturing the compressor housing for a turbocharger according to Modification 1.

FIG. 10 is another conceptual diagram for explaining the method for manufacturing the compressor housing for a turbocharger according to Modification 1.

FIG. 11 is a conceptual diagram for explaining a method for manufacturing a compressor housing for a turbocharger according to Modification 2.

FIG. 12 is another conceptual diagram for explaining the method for manufacturing the compressor housing for a turbocharger according to Modification 2.

DETAILED DESCRIPTION OF THE INVENTION

“Circumferential direction” in the present specification means the rotation direction of a compressor impeller, “shaft direction” means the direction of the rotation shaft of the compressor impeller, “radial direction” means the radius direction of an imaginary circle centered on the rotation shaft of the compressor impeller, and “outside in the radial direction” and “radially outside of” are defined to be in the direction straightly extending from the center of the imaginary circle to the circumference of the circle.

The scroll piece and the shroud piece preferably have in common a contact portion configured to perform positioning at press-fitting by contacting the scroll piece and the shroud piece in a state of opposing in the shaft direction. In this case, the contact portion performs positioning of the scroll piece and the shroud piece in the shaft direction Y serving as a press-fitting direction, whereby the assembling precision of the scroll piece and the shroud piece can be improved.

A method for manufacturing the compressor housing for a turbocharger preferably includes molding the scroll piece and the shroud piece by die-casting; forming the first and second press-fitted portions in the scroll piece, and the first and second press-fitting portions and the communication part in the shroud piece, respectively by machining; and assembling the shroud piece into the scroll piece while forming the refrigerant flow path and the recirculation part by forming the inner circumferential seal part and the outer circumferential seal part, the inner circumferential seal part being formed by press-fitting the first press-fitting portion into the first press-fitted portion, and the outer circumferential seal part being formed by press-fitting the second press-fitting portion into the second press-fitted portion. In this case, only by molding the scroll piece and the shroud piece by die-casting, forming the first and second press-fitted portions in the scroll piece, and the first and second press-fitting portions and the communication part in the shroud piece, respectively by machining, thereafter by press-fitting the shroud piece into the scroll piece to assemble the both, the refrigerant flow path can be sealed on the inner circumferential side of the refrigerant flow path and on the outer circumferential side of the refrigerant flow path while forming recirculation part. Consequently, it becomes unnecessary to interpose an O-ring between the first flow-path formation part and the second flow-path formation part, and the assembling workability is made satisfactory. Further, because the O-ring itself is not necessary, reduction of the parts count can be achieved.

EMBODIMENTS Embodiment 1

Hereinafter, embodiments of the aforementioned compressor housing for a turbocharger will be described with reference to FIGS. 1 to 7.

As shown in FIG. 1, a compressor housing 1 for a turbocharger houses a compressor impeller 13, and is provided with an intake port formation part 10, a shroud part 20, a diffuser part 30, a scroll chamber formation part 120, a refrigerant flow path 5, and a recirculation part 6.

The intake port formation part 10 forms an intake port 11 configured to suck in air toward the compressor impeller 13.

The shroud part 20 surrounds the compressor impeller 13 in the circumferential direction and has a shroud surface 21 facing the compressor impeller 13.

The diffuser part 30 is formed on the outer peripheral side of the compressor impeller 13 in the circumferential direction, and forms a diffuser passage 15 that allows compressed air discharged from the compressor impeller 13 to pass therethrough.

The scroll chamber formation part 120 forms a scroll chamber 12 for guiding the compressed air having passed through the diffuser passage 15 to the outside.

The refrigerant flow path 5 is formed along the diffuser part 30 in the circumferential direction, and allows a refrigerant for cooling the diffuser part 30 to pass therethrough.

The recirculation part 6 is configured to recirculate part of the air, which has been sucked in from the intake port 11 and reached the shroud part 20, to the upstream of the compressor impeller 13.

The compressor housing 1 for a turbocharger is dividably composed of a scroll piece 2 including at least part of the intake port formation part 10 and at least part of the scroll chamber formation part 120, and a shroud piece 3 including at least part of the scroll chamber formation part 120, the diffuser part 30, and the shroud part 20, and being inserted in the inner side of the scroll piece 2.

As shown in FIGS. 1 and 3, the refrigerant flow path 5 is formed as an annular space 50 that is defined by a first flow-path formation part 51 of the scroll piece 2 and a second flow-path formation part 52 of the shroud piece 3, the first flow-path formation part 51 and the second flow-path formation part 52 being formed respectively at each opposing part of the scroll piece 2 and the shroud piece 3 which oppose each other.

The first flow-path formation part 51 and the second flow-path formation part 52 are fitted with each other at an inner circumferential seal part 53 configured to seal the refrigerant flow path 5 on the inner circumferential side of the refrigerant flow path 5 and at an outer circumferential seal part 54 configured to seal the refrigerant flow path 5 on the outer circumferential side of the refrigerant flow path 5.

The inner circumferential seal part 53 is formed by press-fitting a first press-fitting portion 53 b of the shroud piece 3 into a first press-fitted portion 53 a of the scroll piece 2.

The outer circumferential seal part 54 is formed by press-fitting a second press-fitting portion 54 b of the shroud piece 3 into a second press-fitted portion 54 a of the scroll piece 2.

Further, as shown in FIG. 1, the recirculation part 6 includes a recirculation chamber 60 as a space that is defined by a first recirculation chamber formation part 61 of the scroll piece 2 and a second recirculation chamber formation part 62 of the shroud piece 3, the first recirculation chamber formation part 61 and the second recirculation chamber formation part 62 being formed respectively at each opposing part of the scroll piece 2 and the shroud piece 3 which oppose each other; a communication part 63 that is open at the shroud surface 21 and is communicated with the recirculation chamber 60; and a blowout part 64 that is open at the scroll piece 2, or in the upstream position of the compressor impeller 13 of the shroud piece 3, and is communicated with the recirculation chamber 60.

Hereinafter, the compressor housing 1 for a turbocharger according to the present embodiment will be described in detail.

As shown in FIG. 1, the compressor housing 1 is dividably formed of the scroll piece 2 and the shroud piece 3 each prepared separately. The compressor housing 1 is attached to a flange part, or a seal plate 40 formed in the case of dividable structure, of a bearing housing (not shown in any figure) that houses a bearing unit for bearing a shaft 14 on one end of which the compressor impeller 13 is attached.

The scroll piece 2, as shown in FIGS. 1 and 3, includes the intake port formation part 10, a first scroll chamber formation part 121, an outer peripheral portion 125, and a first flow-path formation part 51, a first recirculation chamber formation part 61, and a blowout part 64. The intake port formation part 10 has a cylindrical shape penetratingly formed in the shaft direction Y. The first scroll chamber formation part 121 constitutes a wall surface of the scroll chamber 12 on the intake side Y1. As shown in FIG. 1, the outer peripheral portion 125 is located on the side Y2 that is opposite to the intake side Y1 as an outer peripheral portion of the compressor housing 1. Inside of the outer peripheral portion 125, the seal plate 40 is attached.

As shown in FIG. 1, the first flow-path formation part 51 of the scroll piece 2 is configured to define the refrigerant flow path 5 with the second flow-path formation part 52 to be described later. As shown in FIG. 3, the first flow-path formation part 51 has a first wall surface 511 corresponding to the wall surface of the refrigerant flow path 5 on the intake side Y1. In the present embodiment, the first wall surface 511 forms a surface parallel to the radial direction. Note that the first wall surface 511 is not necessarily flat, and may be recessed toward the intake side Y1.

As shown in FIGS. 1 and 2, the first flow-path formation part 51 has the first press-fitted portion 53 a formed on the inner circumferential side thereof, into which the first press-fitting portion 53 b of the shroud piece 3, which is later described, is press-fitted. The first press-fitting portion 53 b is press-fitted into the first press-fitted portion 53 a to thereby form the inner circumferential seal part 53. As shown in FIG. 2, the first press-fitted part 53 a and the first press-fitting portion 53 b abut on each other throughout the entire circumference.

As shown in FIG. 1, an outer circumference part of the second flow-path formation part 52 of the shroud piece 3 to be described later is press-fitted into the inner circumference of the first scroll chamber formation part 121 of the scroll piece 2. As a result, the second press-fitting portion 54 b as an outer circumference part of the second flow-path formation part 52 is press-fitted into the second press-fitted portion 54 a as an inner circumference part of the first scroll chamber formation part 121 to form the outer circumferential seal part 54. As shown in FIG. 3, the second press-fitted part 54 a and the second press-fitting portion 54 b abut on each other throughout the entire circumference. An interference of the inner circumferential seal part 53 and the outer circumferential seal part 54 is not specifically limited, and can be determined as appropriate considering the stress generated at the inner circumferential seal part 53 and the outer circumferential seal part 54. In the present embodiment, the interference of the both is set to the same magnitude.

One or both of the inner circumferential seal part 53 and the outer circumferential seal part 54 may be preferably provided with a sealing material. Although the kinds of the seal material are not specifically limited, quickly dryable ones are preferable. For example, sealing materials to be used as a liquid gasket can be used.

As shown in FIGS. 1 and 2, the scroll piece 2 includes a refrigerant feed part 58 and a refrigerant discharging part 59 formed of a penetration hole that penetrates the first flow-path formation part 51 to communicate with the refrigerant flow path 5. The refrigerant feed part 58 is configured to feed the refrigerant to the refrigerant flow path 5, and the refrigerant discharging part 59 is configured to discharge the refrigerant therefrom. In the present embodiment, as shown in FIG. 1, the refrigerant feed part 58 and the refrigerant discharging part 59 extend from the first wall surface 511 toward the intake side Y1 in parallel to the shaft direction Y.

As shown in FIGS. 1 and 7, the scroll piece 2 has a first contact surface 561 forming a wall surface parallel to the radial direction, outside of the outer circumferential seal part 54 in the radial direction and inside of the scroll chamber 12.

As shown in FIG. 1, the first recirculation chamber formation part 61 of the scroll piece 2 is formed of a groove that is recessed to the intake side Y1 at its opposing part facing the shroud piece 3 in the shaft direction Y. The blowout part 64 is open to the inside of the scroll piece 2 and is communicated with the first recirculation chamber formation part 61. The first recirculation chamber formation part 61 and the blowout part 64 are provided respectively in a plural number, and are arranged in the circumferential direction.

On the other hand, the shroud piece 3 includes, as shown in FIG. 2, a second scroll chamber formation part 122, the shroud part 20, a first diffuser part 35, the second flow-path formation part 52, the second recirculation chamber formation part 62, and the communication part 63. The shroud piece 3 is formed in a cylindrical shape, and is configured so that the first press-fitting portion 53 b and the second press-fitting portion 54 b of the shroud piece 3 are press-fitted into the first press-fitted portion 53 a and the second press-fitted portion 54 a of the scroll piece 2.

As shown in FIG. 1, the second scroll chamber formation part 122 of the shroud piece 3 forms a wall surface of the scroll chamber 12 on the inner circumferential side. The shroud part 20 forms the shroud surface 21 that faces the compressor impeller 13. The first diffuser part 35 forms a diffuser surface 34 that extends from the shroud surface 21 toward the scroll chamber 12.

As shown in FIG. 1, the second flow-path formation part 52 of the shroud piece 3 is configured to form the refrigerant flow path 5 with the aforementioned first flow-path formation part 51, and is formed on the intake side Y1 of the first diffuser part 35. As shown in FIG. 5, the second flow-path formation part 52 has a second wall surface 521 recessively formed toward the Y2 side that is opposite to the intake side Y1. In the present embodiment, the second wall surface 521 is formed in a U-shape in the cross section parallel to the shaft direction Y, and at the same time, forms an annular recess extending in the circumferential direction radially outside of the shroud surface 21 as shown in FIG. 4. As shown in FIGS. 1 and 9, the second flow-path formation part 52 has a second contact surface 562 that forms a wall surface parallel to the radial direction, radially outside of the second wall surface 521. As shown in FIG. 1, the second contact surface 562 is in contact with the first contact surface 561 of the scroll piece 2 as mentioned above. In this way, the refrigerant flow path 5 is formed as the annular space 50 between the first flow-path formation part 51 and the second flow-path formation part 52.

As shown in FIG. 2, the second recirculation chamber formation part 62 of the shroud piece 3 is formed of a groove that is recessed to the side Y2 that is opposite to the intake side Y1 at its opposing part facing the scroll piece 2 in the shaft direction Y. The communication part 63 is open to the shroud surface 21 in a slit shape, and is communicated with the first recirculation chamber formation part 61. The first recirculation chamber formation part 61 and the communication part 63 are provided in a plural number, and are arranged in the circumferential direction.

The shroud piece 3 is fitted into the scroll piece 2 as shown in FIG. 2, so that the first recirculation chamber formation part 61 and the second recirculation chamber formation part 62 form the recirculation chamber 60 as a space formed of the first recirculation chamber formation part 61 and the second recirculation chamber formation part 62 that are opposed to each other as shown in FIG. 1. The communication part 63 is open at the shroud surface 21 to communicate with the recirculation chamber 60. The blowout part 64 is located in an upstream position of the compressor impeller 13, and is communicated with the recirculation chamber 60. Accordingly, the recirculation part 6 is configured such that part of the intake air which has reached the shroud part 20 is sucked into the recirculation chamber 60 through the communication part 63 and is recirculated to the upstream of the compressor impeller 13 from the blowout part 64. Thus, the recirculation part 6 serves as a casing treatment. It is noted that the configuration of the recirculation part 6 is not specifically limited, and any known configuration can be applied, so long as it functions as a casing treatment.

The seal plate 40 includes, as shown in FIG. 1, a third scroll chamber formation part 123, a seal plate insertion portion 41, and a second diffuser part 36. The third scroll chamber formation part 123 forms a wall surface of the scroll chamber 12 on its outer circumference side. The seal plate insertion portion 41 is inserted into the inside of the outer peripheral portion 125. The second diffuser part 36 forms the diffuser part 30 with the first diffuser part 35. The second diffuser part 36 has a facing surface 37 that faces the diffuser surface 34 of the first diffuser part 35 spaced at a predetermined distance. The space formed between the diffuser surface 34 and the facing surface 37 defines the diffuser passage 15.

Next, a method for manufacturing the compressor housing 1 for a turbocharger according to the present embodiment will be described.

The method for manufacturing the compressor housing 1 for a turbocharger includes a molding/forming step S1, and an assembling step S2. Firstly in the molding/forming step S1, the scroll piece 2 and the shroud piece 3 are separately prepared by die casting, as shown in FIG. 2. And, by machining, the first press-fitted portion 53 a and the second press-fitted portion 54 a are formed in the scroll piece 2, the first press-fitting portion 53 b, the second press-fitting portion 54 b, and the communication part are formed in the shroud piece 3.

Subsequently in the assembling step S2, a shroud press-fit portion 31 of the shroud piece 3 is press-fitted into the inside of the intake port formation part 10 of the scroll piece 2 in the direction as shown by an arrow P in FIG. 2, and the second contact surface 562 of the shroud piece 3 is made abut on the first contact surface 561 of the scroll piece 2. In this way, the refrigerant flow path 5 is formed as the annular space 50 between the first flow-path formation part 51 and the second flow-path formation part 52. At the same time, the recirculation chamber 60 is formed between the first recirculation chamber formation part 61 of the scroll piece 2 and the second recirculation chamber formation part 62 of the shroud piece 3, and the recirculation chamber 60 is communicated with the communication part 63 and the blowout part 64 to constitute the recirculation part 6. It is noted that the first flow-path formation part 51 of the scroll piece 2 and the second recirculation chamber formation part 62 of the shroud piece 3 are configured to have a small gap C therebetween so as not to be in contact with each other, as shown in FIG. 1. Accordingly, the first contact surface 561 and the second contact surface 562 are configured to be surely brought into contact with each other.

In this way, by press-fitting the shroud piece 3 into the scroll piece 2, the first press-fitting portion 53 b of the shroud piece 3 is press-fitted into the first press-fitted portion 53 a of the scroll piece 2 to form the inner circumferential seal part 53, and the second press-fitting portion 54 b of the shroud piece 3 is press-fitted into the second press-fitted portion 54 a of the scroll piece 2 to form the outer circumferential seal part 54. And thus, the first flow-path formation part 51 and the second flow-path formation part 52 are sealed in the refrigerant flow path 5. In the present embodiment, the shroud surface 21 is subjected to machining to thereby ensure the molding accuracy. In this way, the compressor housing 1 for a turbocharger as shown in FIG. 1 is manufactured.

In the compressor housing 1 for a turbocharger, a refrigerant introduction tube and a refrigerant discharge tube, which are not shown in any figure, are connected respectively to the refrigerant feed part 58 and the refrigerant discharging part 59 each communicated with the refrigerant flow path 5 as shown in FIGS. 1 and 2. The diffuser surface 34 can be cooled by circulating the refrigerant in the refrigerant flow path 5 via these tubes.

It is noted that the sealing material may be provided at the inner circumferential seal part 53 by applying the sealing material to the first press-fitted portion 53 a or the first press-fitting portion 53 b after the molding/forming step S1, and then performing the assembling step S2. Similarly, the sealing material may be provided at the outer circumferential seal part 54 by applying the sealing material to the second press-fitted portion 54 a or the second press-fitting portion 54 b after the molding/forming step S1, and then performing the assembling step S2.

Hereinafter, operational effects of the compressor housing 1 for a turbocharger according to the present embodiment will be described in detail.

According to the compressor housing 1 for a turbocharger of the present embodiment, the compressor housing 1 for a turbocharger is dividably formed, and the refrigerant flow path 5 is defined by the first flow-path formation part 51 of the scroll piece 2 and the second flow-path formation part 52 of the shroud piece 3, which are formed respectively at each opposing part of the scroll piece 2 and the shroud piece 3 which oppose each other. The inner circumferential seal part 53 and the outer circumferential seal part 54 seal the refrigerant flow path 5 respectively on the inner circumference side and on the outer circumference side. The inner circumferential seal part 53 is formed by press-fitting the first press-fitting portion 53 b of the shroud piece 3 into the first press-fitted portion 53 a of the scroll piece 2, and the outer circumferential seal part 54 is formed by press-fitting the second press-fitting portion 54 b of the shroud piece 3 into the second press-fitted portion 54 a of the scroll piece 2. The recirculation chamber 60 of the recirculation part 6 is formed of a space that is defined by the first recirculation chamber formation part 61 of the scroll piece 2 and the second recirculation chamber formation part 62 of the shroud piece 3, the first recirculation chamber formation part 61 and the second recirculation chamber formation part 62 being formed respectively at each opposing part of the scroll piece 2 and the shroud piece 3 which oppose each other. Such a configuration makes it possible to seal the refrigerant flow path 5 on the inner circumferential side of the refrigerant flow path 5 and on the outer circumferential side of the refrigerant flow path 5 while forming the recirculation part 6, only by press-fitting the shroud piece 3 into the scroll piece 2 to assemble the both. Consequently, it becomes unnecessary to interpose an O-ring between the first flow-path formation part 51 and the second flow-path formation part 52, and the assembling workability is made satisfactory. Further, because the O-ring itself is not necessary, reduction of the parts count can be achieved. Thus, the refrigerant flow path 5 provided in the compressor housing 1 for a turbocharger makes it possible to restrain deposit accumulation in the diffuser passage 15 to thereby achieve high supercharging on high speed rotation side of an engine and to increase the maximum output of the engine.

Moreover, the compressor housing 1 for a turbocharger is provided with the recirculation part 6 that can recirculate part of the air, which has reached the shroud part 20, to the upstream side of the compressor impeller 13. The recirculation part 6 constitutes a so-called casing treatment, therefore even when the flow rate of the compressor impeller 13 is made largely increased in response to high supercharging, the operation range on the low airflow-rate side can be maintained and reduction of the low-speed torque can be prevented. In other words, the compressor housing 1 for a turbocharger according to the present embodiment makes it possible both to maintain the low-speed torque, which is owing to the fact that the operation range on the low airflow-rate side is maintained by the recirculation part 6, and to increase the maximum output, which is owing to the fact that the refrigerant flow path 5 brings about high supercharging.

Furthermore, the compressor housing 1 for a turbocharger is dividably formed and includes the scroll piece 2 and the shroud piece 3. The scroll chamber 12 is formed by assembling at least both the pieces to each other. Such a configuration makes it possible to form the scroll chamber 12 with a circular cross section while forming the scroll chamber formation part 120 in a shape having no undercut part, which enables mold releasing. As a result, the scroll chamber 12 can be more easily formed by die casting while the compression efficiency for the supplied air can be improved.

In addition, the refrigerant flow path 5 in the compressor housing 1 for a turbocharger according to the present embodiment is easily applicable to a conventional compressor housing for a turbocharger because it requires no significant change in the basic configuration of a scroll piece and a shroud piece from the conventional one.

In the present embodiment, the scroll piece 2 includes the refrigerant feed part 58 formed of a penetration hole that communicates with the refrigerant flow path 5 to feed a refrigerant to the refrigerant flow path 5, and the refrigerant discharging part 59 formed of a penetration hole that communicates with the refrigerant flow path 5 to discharge the refrigerant from the refrigerant flow path 5. Such a configuration makes it possible to easily form the refrigerant feed part 58 and the refrigerant discharging part 59 and to surely flow the refrigerant through the refrigerant flow path 5.

In the present embodiment, at least one of the inner circumferential seal part 53 and the outer circumferential seal part 54 may be provided with a sealing material between the scroll piece 2 and the shroud piece 3 to seal a gap therebetween. Such a configuration makes it possible to enhance sealability at least one of the inner circumferential seal part 53 and the outer circumferential seal part 54 thereby preventing leakage of the refrigerant from the refrigerant flow path 5 to increase the reliability.

In the present embodiment, the scroll piece 2 and the shroud piece 3 have in common a contact portion 56 configured to perform positioning at press-fitting by contacting the scroll piece 2 and the shroud piece 3 in a state of opposing in the shaft direction Y. In such a configuration, the contact portion 56 performs positioning of the scroll piece 2 and the shroud piece 3 in the shaft direction Y serving as a press-fitting direction, whereby the assembling precision of the scroll piece 2 and the shroud piece 3 can be improved.

The method for manufacturing the compressor housing 1 for a turbocharger according to the present embodiment includes the molding/forming step S1 of molding the scroll piece 2 and the shroud piece 3 by die-casting and forming the first press-fitted portion 53 a and the second press-fitted portion 54 a in the scroll piece 2, and the first press-fitting portion 53 b, the second press-fitting portion 54 b, and the communication part in the shroud piece 3, respectively by machining; and the assembling step S2 of assembling the shroud piece 3 to the scroll piece 2, while forming the refrigerant flow path 5 composed of the annular space 50, and the recirculation part 6 by forming the inner circumferential seal part 53 and the outer circumferential seal part 54. The inner circumferential seal part 53 is formed by press-fitting the first press-fitting portion 53 b into the first press-fitted portion 53 a, and the outer circumferential seal part 54 is formed by press-fitting the second press-fitting portion 54 b into the second press-fitted portion 54 a. Such a configuration makes it possible to seal the refrigerant flow path 5 on the inner circumferential side of the refrigerant flow path 5 and on the outer circumferential side of the refrigerant flow path 5 while forming the recirculation part 6 only by press-fitting the shroud piece 3 into the scroll piece 2 to assemble both in the assembling step S2 after molding the scroll piece 2 and the shroud piece 3 by die-casting and then forming the first press-fitted portion 53 a and the second press-fitted portion 54 a in the scroll piece 2, and the first press-fitting portion 53 b, the second press-fitting portion 54 b and the communication part 63 in the shroud piece 3, respectively by machining in the molding/forming step S1. Consequently, it becomes unnecessary to interpose an O-ring between the first flow-path formation part 51 and the second flow-path formation part 52, and the assembling workability is made satisfactory. Further, because the O-ring itself is not necessary, reduction of the parts count can be achieved.

In the present embodiment, the compressor housing 1 for a turbocharger is of a two-piece structure that is composed of the scroll piece 2 and the shroud piece 3. The compressor housing 1 may be of a three-piece structure that is composed of the scroll piece 2, the shroud piece 3, and an annular outer circumference piece 4 as in Modification 1 shown in FIG. 8. The annular outer circumference piece 4 is formed in an annular shape, and includes a third scroll chamber formation part 123 and an annular outer circumference piece insertion portion 410. The annular outer circumference piece insertion portion 410 is press-fitted into the outer peripheral portion 125 to form a press-fit part 42. Note that components in Modification 1 equivalent to those in Embodiment 1 are allotted with the same reference numerals to simplify the description.

Hereinafter, a method for manufacturing the compressor housing 1 for a turbocharger according to Modification 1 will be described. First, in the molding/forming step S1, the scroll piece 2 is molded by die-casting in a similar way to that in Embodiment 1 as shown in FIG. 9. Then, an integral piece 3 a is molded by die casting. The integral piece 3 a is composed of the outer circumference part of the shroud piece 3 in Embodiment 1 and the inner circumference part of the annular outer circumference piece 4 with a contour of the annular outer circumference piece 4 both of which are integrated through a connecting portion 4 a. Then, the first press-fitted portion 53 a and the second press-fitted portion 54 a are formed in the scroll piece 2, and the first press-fitting portion 53 b, the second press-fitting portion 54 b, and the communication part 63 are formed in the shroud piece 3, respectively by machining. Thereafter, in the assembling step S2, the integrated piece 3 a is press-fitted into the inside of the scroll piece 2 in the direction indicated by the arrow P. Then, the shroud piece 3 and the annular outer circumference piece 4 are separated from each other by cutting off the connecting portion 4 a shown in FIG. 10 under the state in which the shroud piece 3 and the annular outer circumference piece 4 are press-fitted into the scroll piece 2. In this way, the compressor housing 1 for a turbocharger of Modification 1 is produced.

The compressor housing 1 for a turbocharger according to Modification 1 also exhibits the operational effects equivalent to those in Embodiment 1. An interference of the press-fit part 42 into which the annular outer circumference piece 4 is press-fitted is preferably smaller than those of the inner circumferential seal part 53 and the outer circumferential seal part 54. In this case, the integrated piece 3 a can be easily press-fitted into the scroll piece 2. In addition, misalignment between the press-fit part of the shroud piece 3 (the inner circumferential seal part 53 and the outer circumferential seal part 54) and the press-fit part 42 of the annular outer circumference piece 4 can be absorbed.

In the compressor housing 1 for a turbocharger according to Modification 1, a part of the integrated piece 3 a for constituting the annular outer circumference piece 4 is not brought into contact with the scroll piece 2 in the shaft direction in the assembling step S2 so as to form a gap B, as shown in FIGS. 8 and 10. Accordingly, it is possible to bring the first contact surface 561 into contact with the second contact surface 562 when the integrated piece 3 a is press-fitted. In this way, the integrated piece 3 a can be positioned further accurately when being press-fitted in the shaft direction. In other words, the shroud piece 3 can be positioned in the shaft direction further accurately for completion. Note that it is also possible to accurately position the annular outer circumference piece 4 in the shaft direction by once again press-fitting the annular outer circumference piece 4 that has been separated from the integrated piece 3 a after performing the assembling step S2 to the position so as to abut on the scroll piece 2 in the shaft direction.

It is noted that the refrigerant flow path 5 is formed by die-casting in Embodiment 1, but instead, as in Modification 2 shown in FIG. 11, the second flow-path formation part 52 may be molded by die-casting so as to have a prescribed depth, and then the bottom of the second wall surface 521 that has been recessively formed toward the Y2 side, namely a cut region 52 a corresponding to a portion located most forward on the Y2 side in the second wall surface 521, may be cut in the molding/forming step S1 so that the second flow-path formation part 52 is more deeply recessed as shown in FIG. 12. In Modification 2, the wall thickness of the diffuser part 30 can be ensured to some extent as shown in FIG. 11 when molded by die-casting, so that moldability can be improved. In addition, as shown in FIG. 12, because the refrigerant flow path 5 can be formed at the position close to the diffuser surface 34, the cooling effect for the diffuser surface 34 can be improved to prevent deposit accumulation more effectively. The present embodiment also exhibits the operational effects equivalent to those in Embodiment 1. In addition, the compressor housing 1 may be of a three-piece structure in a similar way to that in Modification 1.

The present disclosure is not limited to the aforementioned embodiment and modifications, and can be applied to various embodiments and modifications within a range that does not deviate from the gist of the present disclosure. 

1. A compressor housing for a turbocharger configured to house a compressor impeller, the compressor housing comprising: an intake port formation part that defines an intake port configured to suck in air toward the compressor impeller; a shroud part that surrounds the compressor impeller in a circumferential direction and has a shroud surface facing the compressor impeller; a diffuser part that is formed on an outer circumferential side of the compressor impeller in the circumferential direction and forms a diffuser passage configured to allow compressed air discharged from the compressor impeller to pass therethrough; a scroll chamber formation part that forms a scroll chamber configured to guide the compressed air passing through the diffuser passage to outside; a refrigerant flow path that is formed along the diffuser part in the circumferential direction, and allows a refrigerant for cooling the diffuser part to pass therethrough; and a recirculation part configured to recirculate part of the air which has been sucked in from the intake port and reached the shroud part to an upstream of the compressor impeller, wherein the compressor housing is dividably composed of a scroll piece including at least part of the intake port formation part and at least part of the scroll chamber formation part, and a shroud piece including at least part of the scroll chamber formation part, the diffuser part, and the shroud part, and being press-fitted into an inside of the scroll piece in a shaft direction, wherein the refrigerant flow path is formed as an annular space that is defined by a first flow-path formation part of the scroll piece and a second flow-path formation part of the shroud piece, the first flow-path formation part and the second flow-path formation part being formed respectively at each opposing part of the scroll piece and the shroud piece which oppose each other, wherein the first flow-path formation part and the second flow-path formation part are fitted with each other at an inner circumferential seal part configured to seal the refrigerant flow path on the inner circumferential side of the refrigerant flow path and at an outer circumferential seal part configured to seal the refrigerant flow path on the outer circumferential side of the refrigerant flow path, wherein the inner circumferential seal part is formed by press-fitting a first press-fitting portion of the shroud piece into a first press-fitted portion of the scroll piece, wherein the outer circumferential seal part is formed by press-fitting a second press-fitting portion of the shroud piece into a second press-fitted portion of the scroll piece, and wherein the recirculation part includes: a recirculation chamber as a space that is defined by a first recirculation chamber formation part of the scroll piece and a second recirculation chamber formation part of the shroud piece, the first recirculation chamber formation part and the second recirculation chamber formation part being formed respectively at each opposing part of the scroll piece and the shroud piece which oppose each other; a communication part that is open at the shroud surface and is communicated with the recirculation chamber; and a blowout part that is open at the scroll piece, or in an upstream position of the compressor impeller of the shroud piece, and is communicated with the recirculation chamber.
 2. The compressor housing for a turbocharger according to claim 1, wherein the scroll piece and the shroud piece have in common a contact portion configured to perform positioning at the press-fitting by contacting the scroll piece and the shroud piece in a state of opposing in a shaft direction.
 3. A method for manufacturing the compressor housing for a turbocharger according to claim 1, the method comprising: molding the scroll piece and the shroud piece by die-casting; forming the first and second press-fitted portions in the scroll piece, and the first and second press-fitting portions and the communication part in the shroud piece, respectively by machining; and assembling the shroud piece into the scroll piece while forming the refrigerant flow path and the recirculation part by forming the inner circumferential seal part and the outer circumferential seal part, the inner circumferential seal part being formed by press-fitting the first press-fitting portion into the first press-fitted portion, and the outer circumferential seal part being formed by press-fitting the second press-fitting portion into the second press-fitted portion.
 4. A method for manufacturing the compressor housing for a turbocharger according to claim 2, the method comprising: molding the scroll piece and the shroud piece by die-casting; forming the first and second press-fitted portions in the scroll piece, and the first and second press-fitting portions and the communication part in the shroud piece, respectively by machining; and assembling the shroud piece into the scroll piece while forming the refrigerant flow path and the recirculation part by forming the inner circumferential seal part and the outer circumferential seal part, the inner circumferential seal part being formed by press-fitting the first press-fitting portion into the first press-fitted portion, and the outer circumferential seal part being formed by press-fitting the second press-fitting portion into the second press-fitted portion. 